Marine propeller



Dec. 5, 1967 c. D. STRANG 3,355,151

MARINE PROPELLER Filed March 8, 1967 M W 2/ /Z United States Patent 3,356,151 MARINE PROPELLER Charles D. Strang, Waukegan, Ill., assignor to Outboard Marine Corporation, Waukegan, 111., a corporation of Delaware Filed Mar. 8, 1967, Ser. No. 621,693 Claims. (Cl. 17013'5.71)

ABSTRACT OF THE DISCLOSURE Disclosed herein is a marine propeller including a hub which is adapted for rearwardly discharging exhaust gases and which has, at the rearward end thereof, an annular ring located in adjacently outwardly spaced relation to the propeller hub and cooperating with the propeller hub to provide one or more passageways serving to deflect water flowing rearwardly about the hub into the exhaust gas stream. The passageways include at least a portion having a rearwardly decreasing flow area which is effective to produce a hydraulic seal around the adjacent outer periphery of the propeller hub, thereby preventing forward migration along the outer surface of the propeller hub of any low pressure condition at the rear of the propeller hub.

Background of invention- The invention relates generally to marine propellers and particularly to marine propellers having a hollow interior passage terminating at a rearwardly located discharge opening for passage, during engine operation, of exhaust gases into the water.

During operation through the water, there is generally developed rearwardly of the propeller hub, 21 region of relatively low pressure. Also during operation, a thin low pressure boundary layer around the hub can also develop. The low pressure condition rearwardly of the hub has a tendency to join with the low pressure boundary layer and afford exhaust gas migration forwardly along the propeller hub between the blades and along the front face of the propeller blades, thereby causing conditions of cavitation or ventilation. Such conditions of cavitation or ventilation prevent the propeller blade from biting into the water with resultant loss of efliciency.

In addition, if excessively low pressure is developed in the region rearwardly of the propeller hub, such excessive low pressures can also result in a drag on the forward movement of the propulsion unit through the water.

Summary of the invention The invention serves to avoid undesirable migration of exhaust gases forwardly of the discharge end of the propeller hub and to avoidthe occurrence of undesirable, excessively low pressure conditions aft of the propeller hub, by conducting at least a portion of the water passing rearwardly around the periphery of the propeller hub through rearwardly decreasing flow area so as to introduce water into the exhaust gas flow rearwardly from the propeller hub, thereby preventing excessively low pressure conditions and restraining forward flow of exhaust gases. The water flowing through the ducts also serves to restrain forward flow of exhaust gases by creating, immediately in front of the ducts and around the propeller hub forwardly of the exhaust gas discharge opening, draulic seal preventing migration of the exhaust gases forwardly along the outer periphery of the hub toward the front face of the propeller blades.

outwardly spaced relation to the rearwardmost periphery of the propeller hub and which is arranged to deflect water radially inwardly into the exhaust gas stream adjacent to the exhaust gas discharge opening.

Other objects and advantages of the invention will become apparent from the following description and the acoompanying drawings of two embodiments of the invention.

In the drawing:

FIGURE 1 is a fragmentary sectional view of a marine propeller which embodies various of the features of the vention and which is taken along line 11 of FIGURE 2;

FIGURE 2 is a rear end view of the propeller shown in FIGURE 1, with the blades omitted;

FIGURE 3 is an enlarged sectional view of a portion of the propeller shown in FIGURE 1; and

FIGURE 4 is an enlarged sectional view of a modified form of construction.

General description Shown in FIGURES 1 and 2 is a fragmentarily illustrated propeller 11 including a hub 13 and a plurality of blades 15. The hub 13 includes an outer, generally cylindrical wall 17 and an inner annular wall 19 which defines an internal cavity 21 adapted for receiving a propeller shaft (not shown). Conventional means (not shown) can be utilized for attaching the propeller shaft to the propeller hub 13.

Between the outer wall 17 and the inner annular wall 19 is an exhaust gas passageway 23 including passageway segments 25 which are defined by a series of radially extending ribs 27 and which discharge or empty into a common passageway portion 29 terminating at the rear of the propeller hub 13 with an exhaust gas discharge opening or outlet 31.

In accordance with the invention, means are provided for creating a hydraulic seal in a region extending circumferentially about the hub 13 forwardly of the exhaust gas discharge opening 31 and for avoiding the development of excessively low pressure conditions in the area or region immediately behind the propeller hub 13. Such means includes the provision of ducts 33 which are formed to provide, at least in part, flow areas decreasing in the rearward direction and which include inlets 35 communieating with the water passing rearwardly around the hub 13 and outlets 37 communicating with the area located immediately reaiwardlyof the hub into which the exhaust gas is discharged. 1

While various arrangements can be employed, in the disclosed construction, such means is provided by a ring 39 or member of other shape which is mounted in outwardly adjacently spaced relation to the rearwardmost peripheral part of the hub 13 by a series of angularly spaced ribs or legs 41 engaged against a shoulder or recess 43 on the outer periphery of the hub 13 and secured in place by suitable means such as screws 45. In addition to supporting the ring 39, the legs 41 also serve in cooperation with the outer surface of the hub 13 and the inner surface 47 of the ring 39 to divide the resulting annular water scoop or passageway into a circumferentially arranged plurality of the ducts 33.

As already noted, the inner surface 47 of the ring or member 39 is designed so that in cooperation with the outer surface of the hub, the resulting ducts 33 are provided with a flow area which decreases rearwardly between the inlets 35 and the outlets 37. Thus as shown in FIGURE 3, the ducts 33 include a portion 49 of decreasing area between the inlet 35 and the outlet 37. Specifically it is noted that inlet 35 is of larger dimension than the outlet 37. Various configurations of decreasing flow area can be employed. Utilization of such decreasing flow areas provides in the area of the inlet 35 and circumferentially around the outer surface of the hub a hydraulic pressure which is greater than at the outlet 37 and greater than in the area immediately aft of the hub so that a hydraulic pressure seal is provided to prevent migration of low pressure conditions forwardly along the periphery of the hub.

As shown best in FIGURE 3, the inner surface 47 of the ring or member 39 is peripherally concavely or spherically formed so as to more effectively direct the entering water rearwardly into the flow of exhaust gases in the low pressure area immediately after the hub 13.

As also shown best in FIGURE 3, the outer surface 53 of the ring is generally convexly or spherically shaped to afford a generally uniform wall thickness between the inner and outer surfaces 47 and 53 and to facilitate water flow inwardly toward the rearwardly directed exhaust gas flow.

The forward end of the ring 39 is spaced outwardly from the hub 13 at a distance beyond the thin boundary layer so as to intercept solid water and divert the solid water into the duct 33. In this regard, as shown best in FIGURE 3, the forward end of the ring includes a leading edge 44 defined in part by a forwardly and outwardly inclined surface 46, which, in fore and aft crosssection, forms a point with the outer surface 53 of the ring 39. The use of such a pointed leading edge helps to capture the solid water for flow through the ducts. The inclined surface 46 also extends the effective inlet area radially outwardly and provides another portion of rearwardly decreasing fiow area.

It is also noted from FIGURE 1 that the legs 41 extend perpendicularly outwardly so as to avoid any tendency to restrict or diminish inward fiow of the Water into the scoops or ducts.

By way of example of the various other configurations that can be used to obtain various of the advantages of the invention, there is shown in FIGURE 4 an alternate construction.

More specifically, there is shown in FIGURE 4, a ring or member 139 of other shape including parallel inner and outer surfaces 147 and 153 which are conically shaped. However, the inner and outer surfaces 147 and 153 can also be in nonparallel relation to each other and at least some of the advantages of the invention can be obtained when using either or both of a convex outer surface and a convex inner surface. As also shown in FIG- URE 4, if desired, the member 139 can extend more rearwardly than the exhaust gas discharge outlet 131 and can extend radially inwardly beyond the radially outermost portion of the exhaust gas discharge outlet 131. As also shown in FIGURE 4, the outer surface 155 of the hub -113 can extend smoothly all the way to the rearward end of the hub 113, rather than including a recess 43 as shown in FIGURE 3.

It is noted that in FIGURE 4, the member 139 forms, together with the hub 113, a duct 133 which has a decreasing fiow area between the inlet 135 and the outlet 137. Specifically, it is noted that the portion 151 of the duct 133 immediately forwardly of the discharge opening 131 decreases in cross section from the inlet 135 to a neck 157 to provide one portion of decreasing flow area.

As also shown in FIGURE 4, the legs 141 include forward edges 142 which are located rearwardly of the leading edge 144 of the member 139. Such location also serves to provide rearwardly of the inlet 135 a decreasing flow area and to avoid any tendency to restrict or diminish inward flow of water into the ducts 133.

In addition, various means other than the legs 41 and screws 45 shown in FIGURE 1 can be employed to connect the member 139 to the hub 1137 Various of the features of the invention are set forth in the following claims.

What is claimed is:

1. In a marine propeller including a hub having at the rearward end thereof an exhaust gas discharge opening and a plurality of blades extending from said hub forwardly of said opening, the improvement comprising a member mounted on said hub in outwardly spaced relation to said hub and adjacent to the rearward end thereof, said member cooperating with said hub to provide a scoop directing water radially inwardly toward the exhaust gases which flow rearwardly from said discharge opening.

2. A marine propeller in accordance with claim 1 wherein said scoop includes a portion of rearwardly decreasing flow area, whereby there is created a greater fluid pressure adjacent the inlet of said scoop than at the outlet of said scoop.

3. In a marine propeller including a hub having at the rearward end thereof an exhaust gas discharge opening and a plurality of blades extending forwardly of said opening, the improvement comprising means [located adjacent to said discharge opening defining a series of circumferentially arranged ducts having forwardly opening inlets and rearwardly opening outlets, said ducts including portions of rearwardly decreasing flow area, whereby there is created a hydraulic seal extending circumferentially around said hub adjacent the rearward end thereof.

4. A marine propeller in accordance with claim 3 wherein said means defining said ducts comprises a ring mounted on said hub in outwardly spaced relation to said hub and adjacent to the rearward end thereof, said ring cooperating with said hub to provide said portions of rearwardly decreasing flow area.

5. In a marine propeller including a hub having, at the rearward end thereof, an exhaust gas discharge opening, and a plurality of blades extending forwardly of said opening, the improvement comprising an annular member having partially spherically shaped inner and outer surfaces, and a series of legs securing said member on said hub in outwardly adjacent relation to the rearward end of said hub and defining between said member and said hub a series of circumferentially arranged ducts each having an inlet, an outlet rearwardly of said inlet, a portion between said inlet and said outlet with a flow area decreasing rearwardly, and a wall defined by said inner surface adapted to deflect water entering into said ducts toward an area immediately behind said hub.

References Cited UNITED STATES PATENTS 2,401,941 6/1946 Lee 170 -135.71x 2,948,252 8/1960 Alexander 17 FOREIGN PATENTS 553,568 2/1923 France.

MARTIN P. SOHWADRON, Primary Examiner.

EVERETTE A. POWELL, JR., Examiner. 

1. IN A MARINE PROPELLER INCLUDING A HUB HAVING AT THE REARWARD END THEREOF AN EXHAUST GAS DISCHARGE OPENING AND A PLURALITY OF BLADES EXTENDING FROM SAID HUB FORWARDLY OF SAID OPENING, THE IMPROVEMENT COMPRISING A MEMBER MOUNTED ON SAID HUB IN OUTWARDLY SPACED RELATION TO SAID HUB AND ADJACENT TO THE REARWARD END THEREOF, SAID MEMBER COOPERATING WITH SAID HUB TO PROVIDE A SCOOP DIRECTING WATER RADIALLY INWARDLY TOWARD THE EXHAUST GASES WHICH FLOW REARWARDLY FROM SAID DISCHARGE OPENING. 